Endogenous opioids may be released following traumatic or ischemic injury of the central nervous system. These opioids may serve as secondary pathophysiologic factors contributing to the neurological disorder which stems from the injury to the central nervous system. Opiate receptor antagonists, such as naloxone, have been used to treat brain or spinal cord injury at dosages in the range of 1 to 10 mg/kg of body weight of the patient.
However, naloxone is neither completely selective nor a pure opiate antagonist in all situations. At low dosages, naloxone has considerable selectivity for the mu-opiate receptor. At higher dosages, naloxone acts on other opiate receptors, including the delta and kappa receptors. Further at higher dosages, naloxone may have effects that are not mediated by opiate receptors.
In order to simplify and enhance the safety of central nervous system protocols, opiate receptor antagonists which exhibit a high degree of specificity for or enhanced activity at a specific opiate receptor are being sought. Also, opiate receptor antagonists which act exclusively as such without producing any undesirable side reactions within the body are preferred.